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139-412: A space elevator , also referred to as a space bridge , star ladder , and orbital lift , is a proposed type of planet-to-space transportation system, often depicted in science fiction. The main component would be a cable (also called a tether ) anchored to the surface and extending into space. An Earth-based space elevator would consist of a cable with one end attached to the surface near the equator and

278-461: A "characteristic length", L c , which is also known as its "self-support length" and is the length of untapered cable it can support in a constant 1 g gravity field. where σ is the stress limit (in pressure units) and ρ is the density of the material. Hypersonic skyhook equations use the material's "specific velocity" which is equal to the maximum tangential velocity a spinning hoop can attain without breaking: For rotating tethers (rotovators)

417-710: A Skyhook, while spacecraft bound for higher orbit, or returning from higher orbit, would use the upper end. In 2000, NASA and Boeing considered a HASTOL concept, where a rotating tether would take payloads from a hypersonic aircraft (at half of orbital velocity) to orbit . A tether satellite is a satellite connected to another by a space tether. A number of satellites have been launched to test tether technologies, with varying degrees of success. There are many different (and overlapping) types of tether. Momentum exchange tethers are one of many applications for space tethers. Momentum exchange tethers come in two types; rotating and non-rotating. A rotating tether will create

556-485: A biological version, Joan Slonczewski 's 2011 novel The Highest Frontier depicts a college student ascending a space elevator constructed of self-healing cables of anthrax bacilli. The engineered bacteria can regrow the cables when severed by space debris. An Earth space elevator cable rotates along with the rotation of the Earth. Therefore, the cable, and objects attached to it, would experience upward centrifugal force in

695-510: A broader audience with the simultaneous publication of Arthur C. Clarke 's novel, The Fountains of Paradise , in which engineers construct a space elevator on top of a mountain peak in the fictional island country of "Taprobane" (loosely based on Sri Lanka , albeit moved south to the Equator), and Charles Sheffield 's first novel, The Web Between the Worlds , also featuring the building of

834-426: A controlled force on the end-masses of the system due to centrifugal acceleration. While the tether system rotates, the objects on either end of the tether will experience continuous acceleration; the magnitude of the acceleration depends on the length of the tether and the rotation rate. Momentum exchange occurs when an end body is released during the rotation. The transfer of momentum to the released object will cause

973-407: A current that can generate either thrust or drag from a planetary magnetic field , in much the same way as an electric motor does. These can be either rotating tethers, or non-rotating tethers , that capture an arriving spacecraft and then release it at a later time into a different orbit with a different velocity. Momentum exchange tethers can be used for orbital maneuvering , or as part of

1112-584: A database (the Space Object Catalog ) of all known rocket launches and objects reaching orbit, including satellites, protective shields and upper-stages of launch vehicles . NASA later published modified versions of the database in two-line element sets , and beginning in the early 1980s, they were republished in the CelesTrak bulletin board system . NORAD trackers who fed the database were aware of other objects in orbit, many of which were

1251-465: A given amount of cable material, the cable's cross section area would need to be designed for the most part in such a way that the stress (i.e., the tension per unit of cross sectional area) is constant along the length of the cable. The constant-stress criterion is a starting point in the design of the cable cross section area as it changes with altitude. Other factors considered in more detailed designs include thickening at altitudes where more space junk

1390-596: A ground-based missile. He stated that the operation, part of Mission Shakti , would defend the country's interests in space. Afterwards, US Air Force Space Command announced they were tracking 270 new pieces of debris but expected the number to grow as data collection continues. On 15 November 2021, the Russian Defense Ministry destroyed Kosmos 1408 orbiting at around 450 km, creating "more than 1,500 pieces of trackable debris and hundreds of thousands of pieces of un-trackable debris" according to

1529-462: A hazard to spacecraft. The smallest objects cause damage akin to sandblasting , especially to solar panels and optics like telescopes or star trackers that cannot easily be protected by a ballistic shield . Below 2,000 km (1,200 mi), pieces of debris are denser than meteoroids . Most are dust from solid rocket motors, surface erosion debris like paint flakes, and frozen coolant from Soviet nuclear-powered satellites . For comparison,

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1668-411: A massive sky ladder to reach the stars as a way to overcome gravity. Decades later, in 1960, Yuri Artsutanov independently developed the concept of a "Cosmic Railway", a space elevator tethered from an orbiting satellite to an anchor on the equator, aiming to provide a safer and more efficient alternative to rockets. In 1966, Isaacs and his colleagues introduced the concept of the 'Sky-Hook', proposing

1807-479: A meter. They thus put the project in "deep freeze" and also keep tabs on any advances in the carbon nanotube field. In 2018, researchers at Japan's Shizuoka University launched STARS-Me, two CubeSats connected by a tether, which a mini-elevator will travel on. The experiment was launched as a test bed for a larger structure. In 2019, the International Academy of Astronautics published "Road to

1946-403: A modular staged tether system maybe used to achieve the same goal. Multiple tethers would be used between stages. The number of tethers would determine the strength of any given cross-section. For rotating tethers not significantly affected by gravity, the thickness also varies, and it can be shown that the area, A, is given as a function of r (the distance from the centre) as follows: where R

2085-671: A number of Sun-synchronous satellites that keep a constant angle between the Sun and the orbital plane , making Earth observation easier with consistent sun angle and lighting. Sun-synchronous orbits are polar , meaning they cross over the polar regions. LEO satellites orbit in many planes, typically up to 15 times a day, causing frequent approaches between objects. The density of satellites – both active and derelict – is much higher in LEO. Orbits are affected by gravitational perturbations (which in LEO include unevenness of

2224-787: A partnership with the Spaceward Foundation (the operator of Elevator:2010), raising the total value of prizes to US$ 400,000. The first European Space Elevator Challenge (EuSEC) to establish a climber structure took place in August 2011. In 2005, "the LiftPort Group of space elevator companies announced that it will be building a carbon nanotube manufacturing plant in Millville, New Jersey , to supply various glass, plastic and metal companies with these strong materials. Although LiftPort hopes to eventually use carbon nanotubes in

2363-688: A planetary-surface-to-orbit / orbit-to-escape-velocity space transportation system. This is typically a non-conductive tether that accurately maintains a set distance between multiple space vehicles flying in formation. A form of solar wind sail with electrically charged tethers that will be pushed by the momentum of solar wind ions . A concept for suspending an object from a tether orbiting in space. Many uses for space tethers have been proposed, including deployment as space elevators , as skyhooks , and for doing propellant-free orbital transfers. Konstantin Tsiolkovsky (1857–1935) once proposed

2502-531: A protective coating is needed, including relative to UV and atomic oxygen . For applications that exert high tensile forces on the tether, the materials need to be strong and light. Some current tether designs use crystalline plastics such as ultra-high-molecular-weight polyethylene , aramid or carbon fiber . A possible future material would be carbon nanotubes , which have an estimated tensile strength between 140 and 177  GPa (20.3 and 25.7 million psi; 1.38 and 1.75 million atm), and

2641-547: A proven tensile strength in the range 50–60 GPa (7.3–8.7 million psi; 490,000–590,000 atm) for some individual nanotubes. (A number of other materials obtain 10 to 20 GPa (1.5 to 2.9 million psi; 99,000 to 197,000 atm) in some samples on the nano scale, but translating such strengths to the macro scale has been challenging so far, with, as of 2011, CNT-based ropes being an order of magnitude less strong, not yet stronger than more conventional carbon fiber on that scale). For some applications,

2780-734: A result of space weather . These longer-term effects can increase drag at lower altitudes; the 1990s expansion was a factor in reduced debris density. Another factor was fewer launches by Russia; the Soviet Union made most of their launches in the 1970s and 1980s. At higher altitudes, where air drag is less significant, orbital decay takes longer. Slight atmospheric drag , lunar perturbations , Earth's gravity perturbations, solar wind , and solar radiation pressure can gradually bring debris down to lower altitudes (where it decays), but at very high altitudes this may take centuries. Although high-altitude orbits are less commonly used than LEO and

2919-458: A risk to spacecraft. Space debris is typically a negative externality . It creates an external cost on others from the initial action to launch or use a spacecraft in near-Earth orbit, a cost that is typically not taken into account nor fully accounted for by the launcher or payload owner. Several spacecraft, both crewed and un-crewed, have been damaged or destroyed by space debris. The measurement, mitigation, and potential removal of debris

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3058-640: A satellite in geostationary orbit with a cable extending to Earth. The space elevator concept reached America in 1975 when Jerome Pearson began researching the idea, inspired by Arthur C. Clarke 's 1969 speech before Congress. After working as an engineer for NASA and the Air Force Research Laboratory, he developed a design for an "Orbital Tower", intended to harness Earth's rotational energy to transport supplies into low Earth orbit. In his publication in Acta Astronautica ,

3197-410: A single orbit that is widely used by over 500 satellites ). There is currently 85% pollution in LEO (Low Earth Orbit). This was beginning to change in 2019, and several companies began to deploy the early phases of satellite internet constellations , which will have many universal orbits in LEO with 30 to 50 satellites per orbital plane and altitude. Traditionally, the most populated LEO orbits have been

3336-571: A space elevator built on Mars. In David Gerrold 's 2000 novel, Jumping Off The Planet , a family excursion up the Ecuador "beanstalk" is actually a child-custody kidnapping. Gerrold's book also examines some of the industrial applications of a mature elevator technology. The concept of a space elevator, called the Beanstalk , is also depicted in John Scalzi's 2005 novel Old Man's War . In

3475-431: A space elevator on Earth, with its comparatively high gravity, the cable material would need to be stronger and lighter than currently available materials. For this reason, there has been a focus on the development of new materials that meet the demanding specific strength requirement. For high specific strength, carbon has advantages because it is only the sixth element in the periodic table . Carbon has comparatively few of

3614-479: A space elevator. The first gathering of multiple experts who wanted to investigate this alternative to space flight took place at the 1999 NASA conference 'Advanced Space Infrastructure Workshop on Geostationary Orbiting Tether Space Elevator Concepts'. in Huntsville, Alabama. D.V. Smitherman, Jr., published the findings in August of 2000 under the title Space Elevators: An Advanced Earth-Space Infrastructure for

3753-538: A space elevator. Three years later, in Robert A. Heinlein 's 1982 novel Friday , the principal character mentions a disaster at the “Quito Sky Hook” and makes use of the "Nairobi Beanstalk" in the course of her travels. In Kim Stanley Robinson 's 1993 novel Red Mars , colonists build a space elevator on Mars that allows both for more colonists to arrive and also for natural resources mined there to be able to leave for Earth. Larry Niven 's book Rainbow Mars describes

3892-399: A specific height above the surface of the celestial body, but lower than (A). Instead of rotating end for end, tethers can also be kept straight by the slight difference in the strength of gravity over their length. A non-rotating tether system has a stable orientation that is aligned along the local vertical (of the earth or other body). This can be understood by inspection of the figure on

4031-411: A tether satellite, which can operate on electromagnetic principles as generators , by converting their kinetic energy to electrical energy , or as motors , converting electrical energy to kinetic energy. Electric potential is generated across a conductive tether by its motion through the Earth's magnetic field. The choice of the metal conductor to be used in an electrodynamic tether is determined by

4170-401: A tower so tall that it reached into space, so that it would be held there by the rotation of Earth . However, at the time, there was no realistic way to build it. In 1960, another Russian, Yuri Artsutanov , wrote in greater detail about the idea of a tensile cable to be deployed from a geosynchronous satellite , downwards towards the ground, and upwards away, keeping the cable balanced. This

4309-540: A useful function. These include derelict spacecraft (nonfunctional spacecraft and abandoned launch vehicle stages), mission-related debris, and particularly numerous in-Earth orbit, fragmentation debris from the breakup of derelict rocket bodies and spacecraft. In addition to derelict human-made objects left in orbit, space debris includes fragments from disintegration, erosion , or collisions ; solidified liquids expelled from spacecraft; unburned particles from solid rocket motors; and even paint flecks. Space debris represents

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4448-579: A variety of factors. Primary factors usually include high electrical conductivity and low density . Secondary factors, depending on the application, include cost, strength, and melting point. An electrodynamic tether was profiled in the documentary film Orphans of Apollo as technology that was to be used to keep the Russian space station Mir in orbit. This is the use of a (typically) non-conductive tether to connect multiple spacecraft. Tethered Experiment for Mars inter-Planetary Operations (TEMPO³)

4587-518: A wrench, and a toothbrush. Sunita Williams of STS-116 lost a camera during an EVA. During an STS-120 EVA to reinforce a torn solar panel, a pair of pliers was lost, and in an STS-126 EVA, Heidemarie Stefanyshyn-Piper lost a briefcase-sized tool bag. A significant portion of debris is due to rocket upper stages (e.g. the Inertial Upper Stage ) breaking up due to decomposition of unvented fuel. The first such instance involved

4726-402: Is a proposed 2011 experiment to study the technique. A theoretical type of non-rotating tethered satellite system, it is a concept for providing space-based support to things suspended above an astronomical object. The orbital system is a coupled mass system wherein the upper supporting mass (A) is placed in an orbit around a given celestial body such that it can support a suspended mass (B) at

4865-429: Is c. 3 mm (0.12 in). As of 2020 , there were 8,000 metric tons of debris in orbit, a figure that is expected to increase. In the orbits nearest to Earth – less than 2,000 km (1,200 mi) orbital altitude , referred to as low-Earth orbit (LEO) – there have traditionally been few "universal orbits" that keep a number of spacecraft in particular rings (in contrast to GEO ,

5004-582: Is conducted by some participants in the space industry . As of November 2022 , the US Space Surveillance Network reported 25,857 artificial objects in orbit above the Earth, including 5,465 operational satellites. However, these are just the objects large enough to be tracked and in an orbit that makes tracking possible. Satellite debris that is in a Molniya orbit , such as the Kosmos Oko series, might be too high above

5143-460: Is moving on to. This is the Coriolis force : the climber "drags" (westward) on the cable, as it climbs, and slightly decreases the Earth's rotation speed. The opposite process would occur for descending payloads: the cable is tilted eastward, thus slightly increasing Earth's rotation speed. The overall effect of the centrifugal force acting on the cable would cause it to constantly try to return to

5282-434: Is nearer than most think. This last conclusion is based on a potential process for manufacturing macro-scale single crystal graphene with higher specific strength than carbon nanotubes . A significant difficulty with making a space elevator for the Earth is strength of materials. Since the structure must hold up its own weight in addition to the payload it may carry, the strength to weight ratio, or Specific strength , of

5421-402: Is present, consideration of the point stresses imposed by climbers, and the use of varied materials. To account for these and other factors, modern detailed designs seek to achieve the largest safety margin possible, with as little variation over altitude and time as possible. In simple starting-point designs, that equates to constant-stress. For a constant-stress cable with no safety margin,

5560-573: Is tapered based on tension; it has its maximum at a geostationary orbit and the minimum on the ground. The concept is applicable to other planets and celestial bodies . For locations in the Solar System with weaker gravity than Earth's (such as the Moon or Mars ), the strength-to-density requirements for tether materials are not as problematic. Currently available materials (such as Kevlar ) are strong and light enough that they could be practical as

5699-463: Is the space elevator idea, a type of synchronous tether that would rotate with the Earth. However, given the materials technology of the time, this too was impractical on Earth. In the 1970s, Jerome Pearson independently conceived the idea of a space elevator, sometimes referred to as a synchronous tether, and, in particular, analyzed a lunar elevator that can go through the L1 and L2 points , and this

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5838-585: Is the radius of tether, v is the velocity with respect to the centre, M is the tip mass, δ {\displaystyle \delta } is the material density, and T is the design tensile strength. Integrating the area to give the volume and multiplying by the density and dividing by the payload mass gives a payload mass / tether mass ratio of: where erf is the normal probability error function . Let V r = V / V c {\displaystyle V_{r}=V/V_{c}\,} , then: This equation can be compared with

5977-456: Is theorized that a sufficiently large collision of spacecraft could potentially lead to a cascade effect, or even make some particular low Earth orbits effectively unusable for long term use by orbiting satellites, a phenomenon known as the Kessler syndrome . The theoretical effect is projected to be a theoretical runaway chain reaction of collisions that could occur, exponentially increasing

6116-411: Is very unlikely that multiple redundant cables would be damaged near the same point on the cable, and hence a very large amount of total damage can occur over different parts of the cable before failure occurs. Beanstalks and rotovators are currently limited by the strengths of available materials. Although ultra-high strength plastic fibers ( Kevlar and Spectra ) permit rotovators to pluck masses from

6255-527: The International Space Station (ISS) orbits in the 300–400 kilometres (190–250 mi) range, while the two most recent large debris events, the 2007 Chinese antisatellite weapon test and the 2009 satellite collision , occurred at 800 to 900 kilometres (500 to 560 mi) altitude. The ISS has Whipple shielding to resist damage from small MMOD. However, known debris with a collision chance over 1/10,000 are avoided by maneuvering

6394-806: The USAF Defense Meteorological Satellite Program Flight 13 (DMSP-F13) exploded on orbit, creating at least 149 debris objects, which were expected to remain in orbit for decades. Later that same year, NOAA-16 which had been decommissioned after an anomaly in June 2014, broke apart on orbit into at least 275 pieces. For older programs, such as the Soviet-era Meteor 2 and Kosmos satellites, design flaws resulted in numerous break-ups – at least 68 by 1994 – following decommissioning, resulting in more debris. In addition to

6533-603: The Van Allen belts can have markedly lower life than those that stay in low earth orbit or are kept outside Earth's magnetosphere. Tether properties and materials are dependent on the application. However, there are some common properties. To achieve maximum performance and low cost, tethers would need to be made of materials with the combination of high strength or electrical conductivity and low density. All space tethers are susceptible to space debris or micrometeoroids. Therefore, system designers will need to decide whether or not

6672-401: The lunar surface. It would also be able to hold 100 cargo vehicles, each with a mass of 580 kg (1,280 lb), evenly spaced along the length of the elevator. Other materials that could be used are T1000G carbon fiber, Spectra 2000, or Zylon. For gravity stabilized tethers, to exceed the self-support length the tether material can be tapered so that the cross-sectional area varies with

6811-424: The protons and neutrons which contribute most of the dead weight of any material. Most of the interatomic bonding forces of any element are contributed by only the outer few electrons. For carbon, the strength and stability of those bonds is high compared to the mass of the atom. The challenge in using carbon nanotubes remains to extend to macroscopic sizes the production of such material that are still perfect on

6950-465: The rocket equation , which is proportional to a simple exponent on a velocity, rather than a velocity squared. This difference effectively limits the delta-v that can be obtained from a single tether. In addition the cable shape must be constructed to withstand micrometeorites and space junk . This can be achieved with the use of redundant cables, such as the Hoytether ; redundancy can ensure that it

7089-439: The (upward) centrifugal force. The apparent gravity experienced by an object on the cable is zero at GEO, downward below GEO, and upward above GEO. The apparent gravitational field can be represented this way: where At some point up the cable, the two terms (downward gravity and upward centrifugal force) are equal and opposite. Objects fixed to the cable at that point put no weight on the cable. This altitude (r 1 ) depends on

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7228-552: The Chinese interception of FY-1C , Russian trials of its PL-19 Nudol , the American interception of USA-193 and India's interception of an unstated live satellite . Space debris includes a glove lost by astronaut Ed White on the first American space-walk (EVA), a camera lost by Michael Collins near Gemini 10 , a thermal blanket lost during STS-88, garbage bags jettisoned by Soviet cosmonauts during Mir 's 15-year life,

7367-558: The Earth's gravitational field due to variations in the density of the planet), and collisions can occur from any direction. The average impact speed of collisions in Low Earth Orbit is 10 km/s with maximums reaching above 14 km/s due to orbital eccentricity . The 2009 satellite collision occurred at a closing speed of 11.7 km/s (26,000 mph), creating over 2,000 large debris fragments. These debris cross many other orbits and increase debris collision risk. It

7506-460: The Earth's rotation creates upward centrifugal force on the counterweight. The counterweight is held down by the cable while the cable is held up and taut by the counterweight. The base station anchors the whole system to the surface of the Earth. Climbers climb up and down the cable with cargo. Modern concepts for the base station/anchor are typically mobile stations, large oceangoing vessels or other mobile platforms. Mobile base stations would have

7645-488: The Earth's surface. The cable would need to be made of a material with a high tensile strength/density ratio . For example, the Edwards space elevator design assumes a cable material with a tensile strength of at least 100 gigapascals . Since Edwards consistently assumed the density of his carbon nanotube cable to be 1300 kg/m, that implies a specific strength of 77 megapascal/(kg/m). This value takes into consideration

7784-582: The European Space Agency altered the orbit of one of its three Swarm mission spacecraft, based on data from the US Joint Space Operations Center , to lower the risk of collision from Cosmos-375, a derelict Russian satellite. Crewed flights are particularly vulnerable to space debris conjunctions in the orbital path of the spacecraft. Occasional avoidance maneuvers or longer-term space debris wear have affected

7923-574: The GEO level after an 8-day trip. Further details were published in 2016. In 2013, the International Academy of Astronautics published a technological feasibility assessment which concluded that the critical capability improvement needed was the tether material, which was projected to achieve the necessary specific strength within 20 years. The four-year long study looked into many facets of space elevator development including missions, development schedules, financial investments, revenue flow, and benefits. It

8062-512: The NORAD database became publicly available during the 1970s, techniques developed for the asteroid-belt were applied to the study of known artificial satellite objects. Time and natural gravitational/atmospheric effects help to clear space debris. A variety of technological approaches have also been proposed, though most have not been implemented. A number of scholars have observed that systemic factors, political, legal, economic, and cultural, are

8201-695: The New Millennium , concluding that the space elevator could not be built for at least another 50 years due to concerns about the cable's material, deployment, and upkeep. Dr. B.C. Edwards suggested that a 100,000 km (62,000 mi) long paper-thin ribbon, utilizing a carbon nanotube composite material could solve the tether issue due to their high tensile strength and low weight The proposed wide-thin ribbon-like cross-section shape instead of earlier circular cross-section concepts would increase survivability against meteoroid impacts. With support from NASA Institute for Advanced Concepts (NIAC), his work

8340-652: The Northern Hemisphere to be tracked. As of January 2019 , more than 128 million pieces of debris smaller than 1 cm (0.4 in), about 900,000 pieces of debris 1–10 cm, and around 34,000 of pieces larger than 10 cm (3.9 in) were estimated to be in orbit around the Earth. When the smallest objects of artificial space debris (paint flecks, solid rocket exhaust particles, etc.) are grouped with micrometeoroids , they are together sometimes referred to by space agencies as MMOD (Micrometeoroid and Orbital Debris). Collisions with debris have become

8479-522: The Russian Ekspress-AM11 communications satellite was struck by an unknown object and rendered inoperable. On 13 October 2009, Terra suffered a single battery cell failure anomaly and a battery heater control anomaly which were subsequently considered likely the result of an MMOD strike. On 12 March 2010, Aura lost power from one-half of one of its 11 solar panels and this was also attributed to an MMOD strike. On 22 May 2013, GOES 13

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8618-544: The Space Elevator Era", a study report summarizing the assessment of the space elevator as of summer 2018. The essence is that a broad group of space professionals gathered and assessed the status of the space elevator development, each contributing their expertise and coming to similar conclusions: (a) Earth Space Elevators seem feasible, reinforcing the IAA 2013 study conclusion (b) Space Elevator development initiation

8757-524: The Space Shuttle's solid rocket boosters or the Apollo program 's Saturn IB launch vehicles, do not reach orbit. Examples: A former source of debris was anti-satellite weapons (ASATs) testing by the U.S. and Soviet Union during the 1960s and 1970s. North American Aerospace Defense Command (NORAD) only collected data for Soviet tests, and debris from U.S. tests were identified subsequently. By

8896-429: The Sun, wear from low-mass impacts. Even small impacts can produce a cloud of plasma which is an electrical risk to the panels. Satellites are believed to have been destroyed by micrometeorites and (small) orbital debris (MMOD). The earliest suspected loss was of Kosmos 1275 , which disappeared on 24 July 1981 (a month after launch). Kosmos contained no volatile fuel, therefore, there appeared to be nothing internal to

9035-717: The U.S. launched an SM-3 missile from the USS Lake Erie to destroy a defective U.S. spy satellite thought to be carrying 450 kg (1,000 lb) of toxic hydrazine propellant. The event occurred at about 250 km (155 mi), and the resulting debris has a perigee of 250 km (155 mi) or lower. The missile was aimed to minimize the amount of debris, which (according to Pentagon Strategic Command chief Kevin Chilton) had decayed by early 2009. On 27 March 2019, Indian Prime Minister Narendra Modi announced that India shot down one of its own LEO satellites with

9174-553: The US State Department. The vulnerability of satellites to debris and the possibility of attacking LEO satellites to create debris clouds has triggered speculation that it is possible for countries unable to make a precision attack. An attack on a satellite of 10 t (22,000 lb) or more would heavily damage the LEO environment. Space junk can be a hazard to active satellites and spacecraft. It has been suggested that Earth orbit could even become impassable if

9313-510: The accidental creation of debris, some has been made intentionally through the deliberate destruction of satellites. This has been done as a test of anti-satellite or anti-ballistic missile technology, or to prevent a sensitive satellite from being examined by a foreign power. The United States has conducted over 30 anti-satellite weapons tests (ASATs), the Soviet Union / Russia has performed at least 27, China has performed 10 and India has performed at least one. The most recent ASATs were

9452-414: The advantage of being able to be at high altitudes, such as on top of mountains. In an alternate concept, the base station could be a tower, forming a space elevator which comprises both a compression tower close to the surface, and a tether structure at higher altitudes. Combining a compression structure with a tension structure would reduce loads from the atmosphere at the Earth end of the tether, and reduce

9591-425: The advantage over the earlier stationary concepts (with land-based anchors) by being able to maneuver to avoid high winds, storms, and space debris . Oceanic anchor points are also typically in international waters , simplifying and reducing the cost of negotiating territory use for the base station. Stationary land-based platforms would have simpler and less costly logistical access to the base. They also would have

9730-410: The anchor in the western equatorial Pacific, construction costs, construction schedule, and environmental hazards. Additionally, he researched the structural integrity and load-bearing capabilities of space elevator cables, emphasizing their need for high tensile strength and resilience. His space elevator concept never reached NIAC's third phase, which he attributed to submitting his final proposal during

9869-483: The booster move away from its payload and vent any propellant remaining in its tanks. This eliminated one source for pressure buildup in the tanks which had previously caused them to explode and create additional orbital debris. Other countries were slower to adopt this measure and, due especially to a number of launches by the Soviet Union , the problem grew throughout the decade. A new battery of studies followed as NASA, NORAD, and others attempted to better understand

10008-438: The cable below that level would initially accelerate downward along the cable. Then gradually it would deflect eastward from the cable. On the cable above the level of stationary orbit, upward centrifugal force would be greater than downward gravity, so the apparent gravity would pull objects attached to the cable upward . Any object released from the cable above the geosynchronous level would initially accelerate upward along

10147-444: The cable beyond GEO, allowing it to obtain higher speed at jettison. If released from 100,000 km, the payload would have enough speed to reach the asteroid belt. As a payload is lifted up a space elevator, it would gain not only altitude, but horizontal speed (angular momentum) as well. The angular momentum is taken from the Earth's rotation. As the climber ascends, it is initially moving slower than each successive part of cable it

10286-410: The cable increases with altitude, proportional to distance from the center of the Earth, reaching low orbital speed at a point approximately 66 percent of the height between the surface and geostationary orbit, or a height of about 23,400 km. A payload released at this point would go into a highly eccentric elliptical orbit, staying just barely clear from atmospheric reentry, with the periapsis at

10425-425: The cable there to pull upward on it. Because the counterweight, above GEO, is rotating about the Earth faster than the natural orbital speed for that altitude, it exerts a centrifugal pull on the cable and thus holds the whole system aloft. The net force for objects attached to the cable is called the apparent gravitational field . The apparent gravitational field for attached objects is the (downward) gravity minus

10564-403: The cable with friction. Climbers would need to be paced at optimal timings so as to minimize cable stress and oscillations and to maximize throughput. Lighter climbers could be sent up more often, with several going up at the same time. This would increase throughput somewhat, but would lower the mass of each individual payload. The horizontal speed, i.e. due to orbital rotation, of each part of

10703-502: The cable would be thickest at geostationary orbit where tension is greatest, and narrowest at the tips to minimize weight per unit area. He proposed extending a counterweight to 144,000 kilometers (89,000 miles) as without a large counterweight, the upper cable would need to be longer due to the way gravitational and centrifugal forces change with distance from Earth. His analysis included the Moon's gravity, wind, and moving payloads. Building

10842-486: The cable. Then gradually it would deflect westward from the cable. Historically, the main technical problem has been considered the ability of the cable to hold up, with tension, the weight of itself below any given point. The greatest tension on a space elevator cable is at the point of geostationary orbit, 35,786 km (22,236 mi) above the Earth's equator. This means that the cable material, combined with its design, must be strong enough to hold up its own weight from

10981-419: The cascade would begin about 2015. The National Academy of Sciences, summarizing the professional view, noted widespread agreement that two bands of LEO space – 900 to 1,000 km (620 mi) and 1,500 km (930 mi) – were already past critical density. In the 2009 CEAS European Air and Space Conference, University of Southampton researcher Hugh Lewis predicted that

11120-477: The climbers would need to gain a large amount of potential energy as quickly as possible to clear the cable for the next payload. Space tether Tether satellites might be used for various purposes, including research into tether propulsion , tidal stabilization and orbital plasma dynamics. Five main techniques for employing space tethers are in development: Electrodynamic tethers are primarily used for propulsion. These are conducting tethers that carry

11259-472: The company's lofty space elevator ambitions, even after receiving more than $ 200,000 in seed funding. The carbon nanotube manufacturing facility that Liftport announced in 2005 was never built. In 2007, Elevator:2010 held the 2007 Space Elevator games, which featured US$ 500,000 awards for each of the two competitions ($ 1,000,000 total), as well as an additional $ 4,000,000 to be awarded over the next five years for space elevator related technologies. No teams won

11398-549: The competition, but a team from MIT entered the first 2-gram (0.07 oz), 100-percent carbon nanotube entry into the competition. Japan held an international conference in November 2008 to draw up a timetable for building the elevator. In 2012, the Obayashi Corporation announced that it could build a space elevator by 2050 using carbon nanotube technology. The design's passenger climber would be able to reach

11537-715: The construction of a 100,000 km (62,000 mi) space elevator, this move will allow it to make money in the short term and conduct research and development into new production methods." Their announced goal was a space elevator launch in 2010. On 13 February 2006, the LiftPort Group announced that, earlier the same month, they had tested a mile of "space-elevator tether" made of carbon-fiber composite strings and fiberglass tape measuring 5 cm (2.0 in) wide and 1 mm (0.039 in) (approx. 13 sheets of paper) thick, lifted with balloons. In April 2019, Liftport CEO Michael Laine admitted little progress has been made on

11676-409: The cross-section-area as a function of distance from Earth's center is given by the following equation: where Safety margin can be accounted for by dividing T by the desired safety factor. Using the above formula, the ratio between the cross-section at geostationary orbit and the cross-section at Earth's surface, known as taper ratio, can be calculated: The taper ratio becomes very large unless

11815-449: The direction opposing the downward gravitational force. The higher up the cable the object is located, the less the gravitational pull of the Earth, and the stronger the upward centrifugal force due to the rotation, so that more centrifugal force opposes less gravity. The centrifugal force and the gravity are balanced at geosynchronous equatorial orbit (GEO). Above GEO, the centrifugal force is stronger than gravity, causing objects attached to

11954-426: The distance into the Earth's gravity field that the cable needs to extend, and thus reduce the critical strength-to-density requirements for the cable material, all other design factors being equal. A space elevator cable would need to carry its own weight as well as the additional weight of climbers. The required strength of the cable would vary along its length. This is because at various points it would have to carry

12093-539: The economic benefit of reducing debris more aggressively than existing government mandates require. In 1979, NASA founded the Orbital Debris Program to research mitigation measures for space debris in Earth orbit. During the 1980s, NASA and other U.S. groups attempted to limit the growth of debris. One trial solution was implemented by McDonnell Douglas in 1981 for the Delta launch vehicle by having

12232-486: The elevator would have required thousands of Space Shuttle trips, though material could be transported once a minimum strength strand reached the ground or be manufactured in space from asteroidal or lunar ore . Pearson's findings, published in Acta Astronautica, caught Clarke's attention and led to technical consultations for Clarke's science fiction novel The Fountains of Paradise (1979), which features

12371-628: The end of its lifespan, studies suggest this is insufficient. Since GEO orbit is too distant to accurately measure objects under 1 m (3 ft 3 in), the nature of the problem is not well known. Satellites could be moved to empty spots in GEO, requiring less maneuvering and making it easier to predict future motion. Satellites or boosters in other orbits, especially stranded in geostationary transfer orbit , are an additional concern due to their typically high crossing velocity. Despite efforts to reduce risk, spacecraft collisions have occurred. The European Space Agency telecom satellite Olympus-1

12510-548: The end of their life. The satellites are then either boosted into a higher, graveyard orbit or a lower, short-term orbit. Nonetheless, satellites that have been properly moved to a higher orbit have an eight-percent probability of puncture and coolant release over a 50-year period. The coolant freezes into droplets of solid sodium-potassium alloy, creating more debris. Despite the use of passivation, or prior to its standardization, many satellites and rocket bodies have exploded or broken apart on orbit. In February 2015, for example,

12649-421: The energetically favorable vertical orientation, so after an object has been lifted on the cable, the counterweight would swing back toward the vertical, a bit like a pendulum. Space elevators and their loads would be designed so that the center of mass is always well-enough above the level of geostationary orbit to hold up the whole system. Lift and descent operations would need to be carefully planned so as to keep

12788-916: The entire weight of the space elevator. An untapered space elevator cable would need a material capable of sustaining a length of 4,960 kilometers (3,080 mi) of its own weight at sea level to reach a geostationary altitude of 35,786 km (22,236 mi) without yielding. Therefore, a material with very high strength and lightness is needed. For comparison, metals like titanium, steel or aluminium alloys have breaking lengths of only 20–30 km (0.2–0.3 MPa/(kg/m)). Modern fiber materials such as kevlar , fiberglass and carbon/graphite fiber have breaking lengths of 100–400 km (1.0–4.0 MPa/(kg/m)). Nanoengineered materials such as carbon nanotubes and, more recently discovered, graphene ribbons (perfect two-dimensional sheets of carbon) are expected to have breaking lengths of 5000–6000 km (50–60 MPa/(kg/m)), and also are able to conduct electrical power. For

12927-406: The feasibility of the idea and gave direction to the study of tethered systems, especially tethered satellites. In 1990, Eagle Sarmont proposed a non-rotating Orbiting Skyhook for an Earth-to-orbit / orbit-to-escape-velocity Space Transportation System in a paper titled "An Orbiting Skyhook: Affordable Access to Space". In this concept a suborbital launch vehicle would fly to the bottom end of

13066-433: The greatest impediment to the cleanup of near-Earth space. There has been little commercial incentive to reduce space debris since the associated cost does not accrue to the entity producing it. Rather, the cost falls to all users of the space environment who benefit from space technology and knowledge. A number of suggestions for increasing incentives to reduce space debris have been made. These would encourage companies to see

13205-409: The improved versions listed here, but these are currently tracked on radar and have predictable orbits. Although thrusters could be used to change the orbit of the system, a tether could also be temporally wiggled in the right place, using less energy, to dodge known pieces of junk. Radiation, including UV radiation tend to degrade tether materials, and reduce lifespan. Tethers that repeatedly traverse

13344-487: The inoperable spacecraft and precession of the orbital plane. Close approaches (within 50 meters) are estimated at one per year. The collision debris pose less short-term risk than from a LEO collision, but the satellite would likely become inoperable. Large objects, such as solar-power satellites , are especially vulnerable to collisions. Although the ITU now requires proof a satellite can be moved out of its orbital slot at

13483-635: The launch of the Transit-4a satellite in 1961. Two hours after insertion, the Ablestar upper stage exploded. Even boosters that don't break apart can be a problem. A major known impact event involved an (intact) Ariane booster. Although NASA and the United States Air Force now require upper-stage passivation, other launchers – such as the Chinese and Russian space agencies – do not. Lower stages, like

13622-413: The lower mass. The system must move at a single speed, so the tether must therefore slow down the lower mass and speed up the upper one. The centrifugal force of the tethered upper body is increased, while that of the lower-altitude body is reduced. This results in the centrifugal force of the upper body and the gravitational force of the lower body being dominant. This difference in forces naturally aligns

13761-424: The mass of the planet and its rotation rate. Setting actual gravity equal to centrifugal acceleration gives: This is 35,786 km (22,236 mi) above Earth's surface, the altitude of geostationary orbit. On the cable below geostationary orbit, downward gravity would be greater than the upward centrifugal force, so the apparent gravity would pull objects attached to the cable downward. Any object released from

13900-465: The material it is made of must be extremely high. Since 1959, most ideas for space elevators have focused on purely tensile structures, with the weight of the system held up from above by centrifugal forces. In the tensile concepts, a space tether reaches from a large mass (the counterweight) beyond geostationary orbit to the ground. This structure is held in tension between Earth and the counterweight like an upside-down plumb bob . The cable thickness

14039-424: The microscopic scale (as microscopic defects are most responsible for material weakness). As of 2014, carbon nanotube technology allowed growing tubes up to a few tenths of meters. In 2014, diamond nanothreads were first synthesized. Since they have strength properties similar to carbon nanotubes, diamond nanothreads were quickly seen as candidate cable material as well. A space elevator cannot be an elevator in

14178-646: The more efficient and lighter the tether can be in relation to the payloads that they can carry. Eventually however, the mass of the tether propulsion system will be limited at the low end by other factors such as momentum storage. Proposed materials include Kevlar , ultra-high-molecular-weight polyethylene , carbon nanotubes and M5 fiber . M5 is a synthetic fiber that is lighter than Kevlar or Spectra. According to Pearson, Levin, Oldson, and Wykes in their article "The Lunar Space Elevator", an M5 ribbon 30 mm (1.2 in) wide and 0.023 mm (0.91 mils) thick, would be able to support 2,000 kg (4,400 lb) on

14317-435: The number and density of space debris in low-Earth orbit, and has been hypothesized to ensue beyond some critical density. Crewed space missions are mostly at 400 km (250 mi) altitude and below, where air drag helps clear zones of fragments. The upper atmosphere is not a fixed density at any particular orbital altitude; it varies as a result of atmospheric tides and expands or contracts over longer time periods as

14456-610: The onset of the problem is slower, the numbers progress toward the critical threshold more quickly. Many communications satellites are in geostationary orbits (GEO), clustering over specific targets and sharing the same orbital path. Although velocities are low between GEO objects, when a satellite becomes derelict (such as Telstar 401 ) it assumes a geosynchronous orbit; its orbital inclination increases about 0.8° and its speed increases about 160 km/h (99 mph) per year. Impact velocity peaks at about 1.5 km/s (0.93 mi/s). Orbital perturbations cause longitude drift of

14595-526: The orbit of most debris within a decade. A de facto moratorium followed the test. China's government was condemned for the military implications and the amount of debris from the 2007 anti-satellite missile test, the largest single space debris incident in history (creating over 2,300 pieces golf-ball size or larger, over 35,000 1 cm (0.4 in) or larger, and one million pieces 1 mm (0.04 in) or larger). The target satellite orbited between 850 km (530 mi) and 882 km (548 mi),

14734-573: The orbital environment, with each adjusting the number of pieces of debris in the critical-mass zone upward. Although in 1981 (when Schefter's article was published) the number of objects was estimated at 5,000, new detectors in the Ground-based Electro-Optical Deep Space Surveillance system found new objects. By the late 1990s, it was thought that most of the 28,000 launched objects had already decayed and about 8,500 remained in orbit. By 2005 this

14873-430: The other end attached to a counterweight in space beyond geostationary orbit (35,786 km altitude). The competing forces of gravity, which is stronger at the lower end, and the upward centrifugal force, which is stronger at the upper end, would result in the cable being held up, under tension, and stationary over a single position on Earth. With the tether deployed, climbers (crawlers) could repeatedly climb up and down

15012-624: The pendulum-like motion of the counterweight around the tether point under control. Climber speed would be limited by the Coriolis force, available power, and by the need to ensure the climber's accelerating force does not break the cable. Climbers would also need to maintain a minimum average speed in order to move material up and down economically and expeditiously. At the speed of a very fast car or train of 300 km/h (190 mph) it will take about 5 days to climb to geosynchronous orbit. Both power and energy are significant issues for climbers –

15151-503: The portion of near-Earth space most densely populated with satellites. Since atmospheric drag is low at that altitude, the debris is slow to return to Earth, and in June 2007 NASA's Terra environmental spacecraft maneuvered to avoid impact from the debris. Brian Weeden, U.S. Air Force officer and Secure World Foundation staff member, noted that the 2007 Chinese satellite explosion created an orbital debris of more than 3,000 separate objects that then required tracking. On 20 February 2008,

15290-411: The result of in-orbit explosions. Some were deliberately caused during anti-satellite weapon (ASAT) testing in the 1960s, and others were the result of rocket stages blowing up in orbit as leftover propellant expanded and ruptured their tanks. More detailed databases and tracking systems were gradually developed, including Gabbard diagrams, to improve the modeling of orbital evolution and decay. When

15429-408: The right where two spacecraft at two different altitudes have been connected by a tether. Normally, each spacecraft would have a balance of gravitational (e.g. F g1 ) and centrifugal (e.g. F c1 ) forces, but when tied together by a tether, these values begin to change with respect to one another. This phenomenon occurs because, without the tether, the higher-altitude mass would travel slower than

15568-451: The risk of collision becomes too great. However, since the risk to spacecraft increases with exposure to high debris densities, it is more accurate to say that LEO would be rendered unusable by orbiting craft. The threat to craft passing through LEO to reach a higher orbit would be much lower owing to the short time span of the crossing. Although spacecraft are typically protected by Whipple shields , solar panels, which are exposed to

15707-471: The risk of spacecraft failures." The report called for international regulations limiting debris and research of disposal methods. As of January 2019 there were estimated to be over 128 million pieces of debris smaller than 1 cm (0.39 in), and approximately 900,000 pieces between 1 and 10 cm. The count of large debris (defined as 10 cm across or larger ) was 34,000 in 2019, and at least 37,000 by June 2023. The technical measurement cut-off

15846-621: The rotating tether to lose energy, and thus lose velocity and altitude. However, using electrodynamic tether thrusting, or ion propulsion the system can then re-boost itself with little or no expenditure of consumable reaction mass. A skyhook is a theoretical class of orbiting tether propulsion intended to lift payloads to high altitudes and speeds. Proposals for skyhooks include designs that employ tethers spinning at hypersonic speed for catching high speed payloads or high altitude aircraft and placing them in orbit. Electrodynamic tethers are long conducting wires, such as one deployed from

15985-455: The same altitude as LEO and the apoapsis at the release height. With increasing release height the orbit would become less eccentric as both periapsis and apoapsis increase, becoming circular at geostationary level. When the payload has reached GEO, the horizontal speed is exactly the speed of a circular orbit at that level, so that if released, it would remain adjacent to that point on the cable. The payload can also continue climbing further up

16124-508: The satellite which could have caused the destructive explosion which took place. However, the case has not been proven and another hypothesis forwarded is that the battery exploded. Tracking showed it broke up, into 300 objects. Many impacts have been confirmed since. For example, on 24 July 1996, the French microsatellite Cerise was hit by fragments of an Ariane 1 H-10 upper-stage booster which exploded in November 1986. On 29 March 2006,

16263-439: The specific strength of the material used approaches 48 (MPa)/(kg/m). Low specific strength materials require very large taper ratios which equates to large (or astronomical) total mass of the cable with associated large or impossible costs. There are a variety of space elevator designs proposed for many planetary bodies. Almost every design includes a base station, a cable, climbers, and a counterweight. For an Earth Space Elevator

16402-608: The station. Space debris began to accumulate in Earth orbit with the launch of the first artificial satellite , Sputnik 1 , into orbit in October, 1957. But even before this event, humans might have produced ejecta that became space debris, as in the August 1957 Pascal B test . Going back further, natural ejecta from Earth has entered orbit. After the launch of Sputnik, the North American Aerospace Defense Command (NORAD) began compiling

16541-791: The surface of the Moon and Mars, a rotovator from these materials cannot lift from the surface of the Earth. In theory, high flying, supersonic (or hypersonic ) aircraft could deliver a payload to a rotovator that dipped into Earth's upper atmosphere briefly at predictable locations throughout the tropic (and temperate) zone of Earth. As of May 2013, all mechanical tethers (orbital and elevators) are on hold until stronger materials are available. Space debris Space debris (also known as space junk , space pollution , space waste , space trash , space garbage , or cosmic debris ) are defunct human-made objects in space – principally in Earth orbit  – which no longer serve

16680-419: The surface up to 35,786 km (22,236 mi). A cable which is thicker in cross section area at that height than at the surface could better hold up its own weight over a longer length. How the cross section area tapers from the maximum at 35,786 km (22,236 mi) to the minimum at the surface is therefore an important design factor for a space elevator cable. To maximize the usable excess strength for

16819-509: The system along the local vertical, as seen in the figure. Objects in low Earth orbit are subjected to noticeable erosion from atomic oxygen due to the high orbital speed with which the molecules strike as well as their high reactivity. This could quickly erode a tether. Simple single-strand tethers are susceptible to micrometeoroids and space junk . Several systems have since been proposed and tested to improve debris resistance: Large pieces of junk would still cut most tethers, including

16958-493: The tensile force on the tether is projected to be less than 65 newtons (15 lbf). Material selection in this case depends on the purpose of the mission and design constraints. Electrodynamic tethers, such as the one used on TSS-1R, may use thin copper wires for high conductivity (see EDT ). There are design equations for certain applications that may be used to aid designers in identifying typical quantities that drive material selection. Space elevator equations typically use

17097-502: The tether by mechanical means, releasing their cargo to and from orbit. The design would permit vehicles to travel directly between a planetary surface, such as the Earth's, and orbit, without the use of large rockets . The idea of the space elevator appears to have developed independently in different times and places. The earliest models originated with two Russian scientists in the late nineteenth century. In his 1895 collection Dreams of Earth and Sky , Konstantin Tsiolkovsky envisioned

17236-477: The tether material for elevators there. Available materials are not strong and light enough to make an Earth space elevator practical. Some sources expect that future advances in carbon nanotubes (CNTs) could lead to a practical design. Other sources believe that CNTs will never be strong enough. Possible future alternatives include boron nitride nanotubes , diamond nanothreads and macro-scale single crystal graphene . In 1979, space elevators were introduced to

17375-486: The threat from space debris would rise 50 percent in the next decade and quadruple in the next 50 years. As of 2009 , more than 13,000 close calls were tracked weekly. A 2011 report by the U.S. National Research Council warned NASA that the amount of orbiting space debris was at a critical level. According to some computer models, the amount of space debris "has reached a tipping point, with enough currently in orbit to continually collide and create even more debris, raising

17514-489: The time the debris problem was understood, widespread ASAT testing had ended. The U.S. Program 437 was shut down in 1975. The U.S. restarted their ASAT programs in the 1980s with the Vought ASM-135 ASAT . A 1985 test destroyed a 1-tonne (2,200 lb) satellite orbiting at 525 km (326 mi), creating thousands of debris larger than 1 cm (0.39 in). At this altitude, atmospheric drag decayed

17653-415: The total load at each point along the length of the cable. In practice this means that the central tether structure needs to be thicker than the tips. Correct tapering ensures that the tensile stress at every point in the cable is exactly the same. For very demanding applications, such as an Earth space elevator, the tapering can reduce the excessive ratios of cable weight to payload weight. In lieu of tapering

17792-407: The typical sense (with moving cables) due to the need for the cable to be significantly wider at the center than at the tips. While various designs employing moving cables have been proposed, most cable designs call for the "elevator" to climb up a stationary cable. Climbers cover a wide range of designs. On elevator designs whose cables are planar ribbons, most propose to use pairs of rollers to hold

17931-560: The upper stage of Vanguard 1's launch rocket and associated piece of debris, are the oldest surviving artificial space objects still in orbit and are expected to be until after the year 2250. As of May 2022 , the Union of Concerned Scientists listed 5,465 operational satellites from a known population of 27,000 pieces of orbital debris tracked by NORAD. Occasionally satellites are left in orbit when they're no longer useful. Many countries require that satellites go through passivation at

18070-403: The value used is the material's 'characteristic velocity' which is the maximum tip velocity a rotating untapered cable can attain without breaking, The characteristic velocity equals the specific velocity multiplied by the square root of two. These values are used in equations similar to the rocket equation and are analogous to specific impulse or exhaust velocity. The higher these values are,

18209-752: The week of the Space Shuttle Columbia disaster. To speed space elevator development, proponents have organized several competitions , similar to the Ansari X Prize , for relevant technologies. Among them are Elevator:2010 , which organized annual competitions for climbers, ribbons and power-beaming systems from 2005 to 2009, the Robogames Space Elevator Ribbon Climbing competition, as well as NASA's Centennial Challenges program, which, in March 2005, announced

18348-401: The weight of the cable below, or provide a downward force to retain the cable and counterweight above. Maximum tension on a space elevator cable would be at geosynchronous altitude so the cable would have to be thickest there and taper as it approaches Earth. Any potential cable design may be characterized by the taper factor – the ratio between the cable's radius at geosynchronous altitude and at

18487-671: Was about 11.7 km/s (7.3 mi/s), or about 42,120 km/h (26,170 mph). Both satellites were destroyed, creating thousands of pieces of new smaller debris, with legal and political liability issues unresolved even years later. On 22 January 2013, BLITS (a Russian laser-ranging satellite) was struck by debris suspected to be from the 2007 Chinese anti-satellite missile test , changing both its orbit and rotation rate. Satellites sometimes perform Collision Avoidance Maneuvers and satellite operators may monitor space debris as part of maneuver planning. For example, in January 2017,

18626-475: Was adjusted upward to 13,000 objects, and a 2006 study increased the number to 19,000 as a result of an ASAT and a satellite collision. In 2011, NASA said that 22,000 objects were being tracked. A 2006 NASA model suggested that if no new launches took place, the environment would retain the then-known population until about 2055, when it would increase on its own. Richard Crowther of Britain's Defence Evaluation and Research Agency said in 2002 that he believed

18765-433: Was found to be possible with materials then existing. In 1977, Hans Moravec and later Robert L. Forward investigated the physics of non-synchronous skyhooks , also known as rotating skyhooks, and performed detailed simulations of tapered rotating tethers that could pick objects off, and place objects onto, the Moon , Mars and other planets , with little loss, or even a net gain of energy. In 1979, NASA examined

18904-463: Was hit by an MMOD which caused it to lose track of the stars that it used to maintain an operational attitude. It took nearly a month for the spacecraft to return to operation. The first major satellite collision occurred on 10 February 2009. The 950 kg (2,090 lb) derelict satellite Kosmos 2251 and the operational 560 kg (1,230 lb) Iridium 33 collided, 500 mi (800 km) over northern Siberia. The relative speed of impact

19043-476: Was involved more than 20 institutions and 50 participants. The Space Elevator NIAC Phase II Final Report, in combination with the book The Space Elevator : A Revolutionary Earth-to-Space Transportation System (Edwards and Westling, 2003) summarized all effort to design a space elevator including deployment scenario, climber design, power delivery system, orbital debris avoidance, anchor system, surviving atomic oxygen , avoiding lightning and hurricanes by locating

19182-428: Was reported that it would be possible to operationally survive smaller impacts and avoid larger impacts, with meteors and space debris, and that the estimated cost of lifting a kilogram of payload to GEO and beyond would be $ 500. In 2014, Google X's Rapid Evaluation R&D team began the design of a Space Elevator, eventually finding that no one had yet manufactured a perfectly formed carbon nanotube strand longer than

19321-573: Was struck by a meteoroid on 11 August 1993 and eventually moved to a graveyard orbit . On 29 March 2006, the Russian Express-AM11 communications satellite was struck by an unknown object and rendered inoperable; its engineers had enough contact time with the satellite to send it into a graveyard orbit. In 1958, the United States of America launched Vanguard I into a medium Earth orbit (MEO). As of October 2009 , it,

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